A syndesmosis is a joint where two bones are held together by thick connective ligaments. For example, the lower ends of the tibia and fibula are connected by the ankle syndesmosis. An ankle syndesmosis injury (high ankle sprain) involves one or more of the ligaments connecting the bottom ends of the tibia and fibula. A high ankle sprain stretches or tears one of these ligaments. A syndesmosis injury involves a stretching or tear in one of the ligaments in the ankle syndesmosis and can lead to ankle instability. In severe tears of the ligaments, the ends of the tibia and fibula can spread apart. Syndesmosis injuries that cause ankle instability may require surgery. Surgical methods can include implantation of syndesmosis screws or tensioned sutures through the fibula and tibia to reduce the syndesmosis.